1. Field of the Invention
The present invention relates to an anti-armor weapon and in particular to an integral cartridge case and venturi nozzle for the launcher.
2. Description of the Prior Art
Man-portable launchers capable of being fired from the shoulder are well known. It is also desirable to have the weapon be as durable as possible, as the battleground provides a hostile environment capable of damaging the weapon.
Shoulder-fired weapons have a launch tube with a cartridge case holding the projectile. The cartridge case attaches to a venturi-type nozzle which extends out the rear of the launch tube for creating an even distribution of exhaust from the propellant used to launch the projectile. Heretofore, the cartridge case and the nozzle have been separate pieces constructed of an alloy, typically an aluminum alloy. The cartridge case and the nozzle were connected with an O-ring fitting into a groove in each piece.
The two piece construction has several shortcomings which may affect the performance of the weapon. Weight is critical as the weapon may be carried for extended periods of time and for extended distances, limiting mobility of the soldier and adding strain and fatigue. Although aluminum is a relatively lightweight metal, any weight saved is critical and a material lighter than aluminum with comparable strength characteristics improves the utility and performance of the weapon.
Shoulder fired weapons typically receive very rough treatment and the aluminum construction of the nozzle leads to nicks and bending of the venturi portion should the venturi portion be impacted from being thrown or dropped or hit by debris. The venturi nozzle's function is to direct and dissipate the propellant gases in a pattern that protects the operator and minimizes the "kick" of the weapon so that it is recoilless. Should the shape of the nozzle to be altered, as may occur if the end of the nozzle portion is impacted, the flow pattern of the exhaust gases may be affected so that the launcher is not necessarily recoilless.
The aluminum cartridge case has heretofore been secured to the launch tube with screws placed around the periphery of the launch tube. The absorption of energy due to the firing of the projectile places stresses on the bolts which can cause very high localized stress to the launch tube. In addition, the bolts may be remove and the cartridge case removed so that the launch tube may be reused. It is not desirable to have the launch tube be reused as the tube may be used by terrorists or enemy forces who recover the tubes left on battlefield.
The projectile is held in the cartridge case by a ring of adhesive. The projectile and launcher are designed so that the projectile releases from the launcher when the shear force at the adhesive joint reaches a predetermined level. This shear force is generated by the system's propellant. However, when firing, the aluminum expands so that the adhesive layer undergoes a peeling force which may exceed the predetermined release level of the adhesive. When this occurs, the projectile releases at the wrong instant and the performance and the reaction of the launcher may be affected. The swelling of the metal cartridge case, known as "slap", also affects the recoilless reaction, so that the launcher may recoil unexpectedly upon launching the projectile. With the metal cartridge it is difficult to improve the tolerances to match the launch tube and difficult to dissipate heat so that the cartridge case does not undergo thermal expansion.
It can be seen then that a man-portable launcher is needed which is rugged and lightweight, and has a cartridge case which minimizes weight, decreases slap, improves reliability and performance and is inexpensive to manufacture.